#include<bits/stdc++.h>
using namespace std;
#define ll long long

int main() {
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    int n; cin >> n;
    int ans = 0;
    while (n) {
        if (n % 10 % 2 == 0) break;
        ans++;
        n /= 10;
    }
    cout << ans << '\n';
    return 0;
}